Stud welding

Weld nut (right) for stud welding.

Stud welding is a form of spot welding where a bolt or specially formed nut is welded onto another metal part. The bolts may be automatically fed into the spot welder. Weld nuts generally have a flange with small nubs that melt to form the weld. Studs have a necked down, unthreaded area for the same purpose.

Weld Studs are used in stud welding systems. Capacitor discharge weld studs range from 14 gauge to 3/8" diameter. They can come in many different lengths ranging from 1/4" to 5" and larger. The tip on the weld end of the stud serves a two-fold purpose:

1. It acts as a timing device to keep the stud off of the base material
2. It disintegrates when the trigger is pulled on the gun.

When the tip disintegrates, it melts and helps solidify the weld to the base material.

Arc studs range from a #8 to 1 1/4" diameter. The lengths are variable from 3/8" to 60" (for deformed bars). Arc studs are typically loaded with an aluminum flux ball on the weld end which aids in the welding process.

Stud welding, also known as stud arc welding, joins a stud and another piece of metal together. The stud is usually joined to a flat plate by using the stud as one of the electrodes. The polarity used in stud welding depends on the type of metal being used. Welding aluminum, for example,would usually require direct-current electrode positive(DCEP). Welding steel would require direct-current electrode negative (DCEN).

Stud welding uses a type of flux called a ferrule, a ceramic ring which concentrates the heat generated, prevents oxidation and retains the molten metal in the weld zone.

Portable stud welding machines are available. Welders can also be automated, with controls for arcing and applying pressure. Stud welding very versatile; typical applications include automobile bodies, electrical panels, shipbuilding and building construction.

A type of stud welding called capacitor-discharge (CD) stud welding differs from regular stud welding in that capacitor-discharge welding does not require flux. The weld time is shorter, enabling the weld to bond with little oxidation and no need for heat concentration. This process uses a direct-current arc from a capacitor. The weld time in this process is between 1 and 6 milliseconds. CD stud welding is often used for smaller diameter studs and pins, as well as on non-standard materials and for accuracy. On the other hand, arc stud welding is primarily for structural purposes and larger diameter weld studs.

References

• Weman, Klas (2003). Welding processes handbook. New York: CRC Press LLC. ISBN 0-8493-1773-8.
• Manufacturing Engineering and Technology Text book fifth edition by serope kalpakjian and steven R. Schmid